Natural agate from a South Island river.
Agate is a term for irregularly- and concentrically-layered masses of microcrystalline quartz. Layers consist of translucent or opaque, microcrystalline, fibrous quartz called chalcedony. Impurities in different layers create different colours such as clearish-whitish-grayish, brownish-red, and yellowish-brown.
Size: Hand specimen.
Locality: South Island, New Zealand.
Images are examples of specimens only. Sizes and shapes may vary.